The Structures Design,Synthesis And Performances Of Organic Conjugated Fluorescent Materials

The organic conjugate fluorescent materials have a wide range of applications in the electrochromic,chemical/biosensor,organic solar cells,biomedical imaging and ion detection as well as other fields due to their excellent photoelectric properties,environmental friendliness and good biocompatibility,etc.The design and synthsis of organic conjugated fluorescent materials with novel structure and excellent performance has become one of the hot topics in the current research of fluorescent materials.In addition,organic conjugated fluorescent materials also have other advantages,such as high physical and chemical stability,convenient modification with functional group and easy processing,so the synthesis of organic conjugated fluorescent materials causes more extensive research interest in the scientific field.In this thesis,the research work fucosed on the design,synthesis and optical as well as electrochemical properties of organic conjugated fluorescent materials.For example,the conjugated oligomers with thiophene and indole moieties have been synthesized,and their photoluminescence and electrochromic performances have been explored.The 8-indole-BODIPY derivatives have been synthesized,and the relationship of their structures and photoluminescence performances has been discussed in detail.Also,the synthesis and photoluminescence modulating of polypyrrole fluorescent nano-spheres/dots have also been studied.The novel results obtained in this thesis were briefly described as follows:(1)Conjugated oligomers with thiophene and indole moieties:synthesis,photoluminescence and electrochromic performancesA series of monomers with thiophene and indole moieties and their corresponding oligomers have been synthesized and characterized by NMR,GPC,FTIR and TGA measurements.The information of structure and formation for these oligomers and the contribution of the increase of indole moieties to their thermal stability were given.The UV and CV results verified that the number and denseness of indoles in the conjugated oligomers and the length of alkyl chains on indole moiety could affect the?-? stacking interaction of conjugated structures in the as-prepared oligomers and lead to the difference in bandgaps and absorption behaviors.This provides us with a valuable approach to predictably tune the frontier molecular orbital energy levels and guide the synthesis of the novel fluorescent materials.The electrochromic device on the basis of the oligomer of poly(1-hexyl-5-(3-thiophene)-1H-indole)exhibited a four-color electrochromic properties and good environmental and redox stability,suggesting its potentiality for application as a novel electrochromic material.Moreover,the oligomer of poly(1-hexyl-5-(3-thiophene)-1H-indole)also can be appropriately applied as selective fluorescence sensor for the detection of Zn2+because of its high sensitivity and selectivity.(2)Synthesis and photoluminescence performances of 8-indole-BODIPY derivativesA series of 8-indole-BODIPY derivatives cl-c6 have been synthesized and characterized by NMR,FTIR and MS measurements.It can be revealed from the crystal structure and spectral properties of c3 that the anti-parallel structure between BODIPY core made the molecule have ?-? interaction with a certain degree,leading to the enhance of the fluorescence quantum yeild.As to c5,due to the introduction of the thiophene ring to the indole ring forming a large planar,the dihedral angle between BODIPY core and the large planar became smaller,resulting in the higher degree of free rotation of the large planar,the fasted vibrational relaxation of electrons in molecules and the larger energy consumption owing to internal conversion,thereby reducing the fluorescence quantum yield.The UV-vis and PL spectra results of the prepared BODIPY compounds in different polar solvents showed that the electron-withdrawing effect and the strong polar solvent made the fluorescence emission peaks blue shift and fluorescence quantum yield decrease,while the electron-donating effect and the weak polarity solvent caused the fluorescence emission peaks red shift and fluorescence quantum yield enhance.Theoretical calculations and CV results showed that the electron-withdrawing groups are favorable for increasing the oxidation potential,and the electron-donating groups contribute to the reduction of the oxidation potential.Due to the influences of NO2 and NH2,c3 and c6 are more sensitive to pH changes.While c1,c2,c4 and c5 are more stable at different pH conditions,which can be attributed to the N of indole ring are easily protonated and deprotonated.Also,another reason may be that the F atom could form hydrogen bonds with BODIPY core inhibiting the destruction of fluoroboric complex under strong alkaline conditions.Moreover,the resultant BODIPY compound can be appropriately applied as cell imaging materials due to their good physical chemical characteristics and excellent biocompatibility.Futhermore,for c6 in mixed solvents of ethanol and glycerol with different proportions,the logarithm of the fluorescence intensity increased linearly with the logarithm of the solvent viscosity,implying that c6 could be expected to be apply to test the intracellular viscosity changes of the living cell for disease diagnosis.(3)Synthesis and photoluminescence modulating of polypyrrole fluorescent nano-spheres/dotsPPy nanospheres with an average diameter of 20 nm have been successfully synthesized by controlling the slow oxidative polymerization of pyrrole in the presence of 3-chloroperbenzoic acid as the oxidizing agent and pure ethanol as the solvent.The as-prepared PPy nanospheres showed an excitation-dependence photoluminescence characteristics and the stable fluorescence intensity under varied ionic strengths and UV excitation time.Through the surface functionization by the different surface passivating agents such as PEG2000,TTDDA and EDA,the quantum yield of the polypyrrole fluorescent nanospheres could be enhanced from its initial value of 2.2%to 3.1%,13%and 40%respectively,which was related to the increased electron density in samples.TEM,UV and CV results demonstrated that 5.5 nm to 3.0 nm sized PPy nanodots were gained after the surface passivation of the PPy nanospheres,and the decrease of sample size was consistent with the decrease of the band gap and the increase of fluorescence lifetime,which was attributed to different degrees of contribution of the electron donating strength of the passivating agents.This provides us with a valuable approach to predictably tune the frontier molecular orbital energy levels and guide the synthesis of new fluorescent emissive materials.Furthermore,these resultant PPy fluorescent nanospheres/dots can be appropriately applied as cell-imaging,and printing ink materials because of their good biocompatibility and high luminescence stability.